okHttp

Factory for calls, which can be used to send HTTP requests and read their responses.

OkHttpClients Should Be Shared

OkHttp performs best when you create a single OkHttpClient instance and reuse it for all of your HTTP calls. This is because each client holds its own connection pool and thread pools. Reusing connections and threads reduces latency and saves memory. Conversely, creating a client for each request wastes resources on idle pools.

Use OkHttpClient() to create a shared instance with the default settings:

// The singleton HTTP client.
val client = OkHttpClient()

Or use okHttp { } to create a shared instance with custom settings:

// The singleton HTTP client.
val client = okHttp {
    addInterceptor(HttpLoggingInterceptor())
    cache(Cache(cacheDir, cacheSize))
}

Customize Your Client With newBuilder()

You can customize a shared OkHttpClient instance with new. This builds a client that shares the same connection pool, thread pools, and configuration. Use the builder methods to configure the derived client for a specific purpose.

This example shows a call with a short 500 millisecond timeout:

val eagerClient = okHttp {
    readTimeout(500, TimeUnit.MILLISECONDS)
}
val response = eagerClient.newCall(request).execute()

Shutdown Isn't Necessary

The threads and connections that are held will be released automatically if they remain idle. But if you are writing an application that needs to aggressively release unused resources you may do so.

Shutdown the dispatcher's executor service with shutdown(). This will also cause future calls to the client to be rejected.

client.dispatcher().executorService().shutdown()

Clear the connection pool with evictAll(). Note that the connection pool's daemon thread may not exit immediately.

client.connectionPool().evictAll()

If your client has a cache, call close(). Note that it is an error to create calls against a cache that is closed, and doing so will cause the call to crash.

client.cache().close()

OkHttp also uses daemon threads for HTTP/2 connections. These will exit automatically if they remain idle.

See also